This is coming from somebody that has no idea about PC gaming or anything with Graphics cards... I was able to play Fire Emblem Path of Radiance for the Gamecube at a consistent 75%. It was not the best, but the game was playable.

However, today I started playing the 2007 Wii game Fire Emblem Radiant Dawn, and it runs only at 50% making it extremely difficult to play. Here are my specs:

MacBook Pro (13-inch, Late 2016, Four Thunderbolt 3 Ports)

Processor: 2.9 GHz Intel Core i5

Memory: 16 GB 2133 MHz LPDDR3

Graphics: Intel Iris Graphics 550 1536 MB

What would be the best settings to get smooth Wii gameplay with this specs?

Switching to Windows using Boot Camp. That will ensure that you get a lot more juice from your laptop. After that, you can download and configure Dolphin as normal (and also setting High Performance after you´re in Windows).